1. Field of the Invention
This invention relates to apparatus for cleaning teeth, and more particularly to an improved apparatus for use in the removal of tenaceous stain and heavy plaque from exposed tooth surfaces by simultaneously directing a stream of air containing entrained cleaning powder and a stream of water onto the tooth surfaces to be cleaned.
2. Description of the Prior Art
While an effective home care program including regular brushing and flossing is considered essential to dental hygiene, such home care normally cannot be completely effective in removing stain and plaque, particularly from relatively inaccessible surfaces between the teeth and from pits and fissures. Accordingly, it is normally recommended that a dental care program include regular, periodic professional cleaning. Such professional cleaning operation conventionally has involved the removal of calculus, particularly from subgingival surfaces, and the cleaning of the exposed enamel surfaces for the removal of stain and plaque. Cleaning the enamel surface normally has involved polishing with an abrasive material, typically pumice, in a paste by use of a rotary rubber cup. This method is effective in cleaning accessible surfaces, but cannot remove all stains from deep pits and fissures, even after protracted use of the pumice and rubber cup.
It has also been known, for example from U.S. Pat. Nos. 3,882,638 and 3,972,123, to employ air-abrasive equipment for cleaning of teeth, using insoluble abrasive particles entrained in an air stream directed onto the tooth surface while simultaneously discharging a water stream in surrounding relation to the air-abrasive stream. The use of soluble abrasive particles or pellets, and of powdered abrasive material, respectively, are also known from U.S. Pat. Nos. 4,214,871 and 4,174,571.
The prior art abrasive cleaning devices which have been most widely used commercially employ water delivered in one or more streams surrounding the air-abrasive stream to form a converging water curtain to provide a wet surface for more effective cleaning, eliminate dust from within the patient's mouth and to dissolve and flush the abrasive material and carry it away for removal by the conventional suction equipment. Although the use of insoluble abrasive material has not met with widespread commercial acceptance, soluble abrasives, particularly a sodium bicarbonate cleaning powder, has been widely accepted and is very effective in cleaning stain and plaque from deep pits and fissures or other surface areas which could not be effectively reached by the rotating rubber brush and pumice technique. However, the reliable feeding of the cleaning powder at a uniform, accurately controllable rate has not always been possible with the prior art devices. For example, U.S. Pat. No. 4,214,871 discloses the use of an aspirator effect to create suction sufficient to lift the soluble abrasive particles from a supply container attached to the apparatus, but discloses no means for metering, or controlling, the rate of flow of the abrasive particles.
U.S. Pat. No. 3,882,638, mentioned above, discloses a cleaning powder supply chamber and dispensing mechanism of a type which has been used on commercial dental cleansing apparatus. This system includes a powder receptacle or chamber including a removable top closure member with an elongated tube projecting through the closure terminating in a closed end positioned adjacent the bottom of the chamber. A concentric sleeve mounted on the closure member projects downwardly in surrounding relation to the tube, the air under pressure admitted to the annular space between the tube and sleeve is discharged through outlets in a spacer member at the bottom of the sleeve. The air pressurizes the chamber and escapes through inlet ports in the bottom portion of the tube, with the escaping air blowing powder from the container into the tube for delivery to an airline connected to the handpiece. Although a bleed-off valve is provided for the abrasive chamber, this valve is closed during operation and all air flowing into the chamber must pass through the ports in the bottom of the tube.
In another prior art dental cleaning apparatus of this general type, manufactured by the assignee of the present invention, a secondary air outlet is provided in the top closure of the powder chamber. The third outlet vents the air space above the body of powder directly to the main air supply line leading to the handpiece. In use of this device, more air can be discharged into the mass of cleaning powder adjacent the bottom of the chamber than passed upward through the central tube to deliver cleaning powder to the handpiece. This excess air passes upward through and fluffs the cleaning powder before escaping through the secondary air outlet. Again, however, air flowing through the body of powder and into the ports in the bottom of the tube was relied on as the primary source of cleaning powder delivered to the handpiece. Variations in air pressure were relied upon to control the abrasive powder flow rate.